I don't have details on the changes to the PC app, but early user reports posted at MobileRead are saying that kobo has made significant improvements with this latest firmware.
Among the changes mentioned: the v3.5 update improved the scrolling animation in the web browser, sped up the sync process, and fixed a number of bugs. There's also a report that the long paragraph bug is fixed, and that this update adds support for the new cursed Adobe DRM. There is also one report that collections are no longer being displayed "in a weird order".
One beta tester also reports that Kobo improved the annotation features, including the changes made in the v3.4.1 firmware (some of which didn't work well). Other subtle changes include the state of the frontlight now being remembered across sleep, power off, and connection to PC (it used to default to off).
The firmware updates should be sent out automatically over the next few weeks, but if you don't want to wait then you can find download links and instructions over on MobileRead.
Here is a partial list of the updates and changes which users and beta testers are reporting:
- Less flashing when scrolling in the browser
- Support for new Adobe DRM
- Better Annotations Experience
- Various Bug Fixes
- Stability Improvements
- Long paragraph bug fixed for Epubs!
- The frontlight returns to the same level as before waking the device from sleep or unplugging from a PC.
- Faster sync.
- If "Track reading activity" is not selected, the reading stats tile is no longer displayed after finishing a book.
- Radio buttons for location replaced with drop-down at end of list
- Sort options in result list